A flap on an aircraft is attached to the wing at each end of the flap. A flap end support must allow for multiple degrees of freedom of movement of the flap whilst supporting the flap throughout that movement. The primary direction of movement of a flap during deployment and stowage may require it to follow an arcuate path. However, in addition to its primary direction of movement, secondary movements in other directions may also occur due to, for example, misalignments caused by wing bending which can induce axial changes in the length of the wing assembly, all of which must be accommodated for in the flap support.
In larger aircraft, the flaps may be required to follow a more unusual and constantly changing three-dimensional arc of movement during deployment so that they effectively extend widthwise (i.e. in a direction extending along the wing) in a direction which is essentially perpendicular to the direction of flow of air across the flap when fully deployed and so assume what is commonly known as a “streamwise” position. This is particularly the case with flaps that are located towards the outboard end of a wing away from the fuselage and which do not extend in a widthwise in a direction along the wing which is perpendicular to the direction of airflow when stowed, due to the tapering nature of the trailing edge of the wing to which they are mounted. This problem is less apparent with a flap located towards the inboard end of the wing closer to the fuselage as this flap may essentially extend in a widthwise direction along the wing and perpendicular to the direction of airflow over the wing when stowed.
Therefore, it may be possible for the inboard flap to follow a two-dimensional path during deployment to maintain a streamwise position.
Traditionally, the conventional structure used to support the end of a flap consists of a complex track and carriage that employs a swinging arm assembly. Although this allows for multiple degrees of freedom of movement of the flap, it is complex because it requires a large number of parts. Its bulk also causes electrical system routing difficulties and increases weight.
The provision of a track which is shaped so as to enable a carriage travelling along the track to follow a path having directional components in three dimensions has been proposed. The track can be mounted either on the falsework rib within the wing structure or, to the end of the flap itself. Although this solution results in a reduction in the number of components, a track which is shaped so as to enable movement of a carriage following the track in three-dimensions is a complex and expensive structure to manufacture and accurate inspection to ensure that it has been accurately made to specified dimensions is difficult to achieve. It has also been found that the multi-roller bearings that follow a three-dimensional track are exposed to higher loads and arc more prone to jamming and experience higher wear rates due to scuffing of the bearing against the surface of the track and/or skidding of the bearing across the track surface, especially when misalignment of the flap occurs due to unusual load patterns.
The provision of adequate failsafe features to ensure continued operation despite failure of any primary components has also been problematic in each of the proposals referred to above.
The present invention seeks to provide a support assembly that substantially overcomes or alleviates the problems and disadvantages described above and to offer considerable advantages over existing solutions in terms of reduced complexity, reduced physical size and weight.